Scroll compressor with rotation preventing apparatus

ABSTRACT

A scroll compressor having a stationary scroll member and a rotary scroll member. The compressor is provided with a mechanism for obtaining an orbital movement of the rotary scroll member while preventing a rotation thereof about its own axis. The mechanism has a stationary and a rotary ring arranged in parallel and spaced from each other. These rings form a plurality of circumferential spaced facing pairs of circular holes. The mechanism also has shoes arranged in the respective holes and balls arranged between the shoes in the facing pair of holes. The shoes can maintain a parallel location with respect to the corresponding holes, since the shoes are movable relative to the ball. A sealtight contact of the rotary scroll member with the stationary scroll member is realized over a prolonged period.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a scroll compressor, and moreparticularly, to a mechanism for obtaining an orbital movement of ascroll member while preventing a rotation thereof about its own axis.

2. Description of the Related Art

Japanese Unexamined Patent Publication (Kokai) No. 59-28082 proposes amechanism for obtaining an orbital movement in a scroll compressor,which includes a housing having a rotary scroll member housed therein Astationary ring and a rotary ring facing each other are arranged betweenthe housing and the rotary scroll member at the facing sides thereof,respectively. Both rings form a plurality of opposite pairs of pocketsand a tubular shaped bearing member arranged between the facing pockets.The arrangement is such that the radius of the orbital movement of therotary scroll member is limited to the sum of the diameter of themovable area of the cylindrical bearing member in one of the oppositepockets and the diameter of the movable area of the cylindrical bearingmember in the other pocket This orbital movement mechanism receives notonly the thrust force in the rotary scroll member but also the radialforce of the rotary scroll member, to prevent a rotation of the rotaryscroll member about its own axis Accordingly, a compressor provided withthis type of orbital movement mechanism has a simplified constructionand requires a smaller number of parts when compared with a conventionaltype compressor provided with separate mechanisms for receiving thethrust force and for preventing self rotation.

In this type of improved mechanism for obtaining an orbital movement, aninclination of the cylindrical bearing member may occur due todisplacement forces applied in opposite radial directions to the ends ofthe cylindrical bearing member during the orbital movement of the rotaryscroll member, where a necessary precise degree of parallelism is notobtained between the end surfaces of the cylindrical bearing member. Inthis situation, the particular limited portions of the cylindricalbearing member, i.e., the edged portions at the ends of the member, cancome into sliding contact with the corresponding housing and the rotaryscroll member, which causes a partial wear of these parts after use fora very short period. Furthermore, even if the necessary precise degreeof parallelism is obtained between the end surfaces of the cylindricalbearing member, wear and tear easily occurs during a very short period,based on the construction that the cylindrical bearing member is inpartial contact, at the circumferential edge portions of the endsthereof, with the corresponding portions of the housing and the rotaryscroll member. Due to this wear and tear, a clearance is generatedbetween the inner surface of the base wall of the stationary scrollmember and the tip end of the scroll portion of the stationary scrollmember, thereby reducing the compression efficiency. Furthermore, thecylindrical bearing member is subjected to a reaction force caused bythe compression at the portion near the outer periphery of the rotaryscroll member, causing the base wall portion of the rotary scroll memberto be bent. This brings the cylindrical bearing member into a greaterpartial contact with the rotary scroll member at the peripheral edgeportions of the cylindrical bearing member, and thus wear and tear isvery easily generated.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a scroll compressor inwhich little wear of the parts occurs.

According to the present invention a scroll compressor is provided whichcomprises:

a housing assembly defining an inlet port for the medium to becompressed and an outlet for the removal thereof;

an axially extending drive shaft rotatably supported in the housingassembly;

a stationary scroll member fixedly arranged in the housing assembly andconcentric to the shaft;

a movable scroll member freely rotatable about an axis which is spacedfrom the axis of the drive shaft;

the movable scroll member being arranged so as to realize an orbitalmovement without a rotation thereof about its own axis;

a plurality of chambers formed between the scroll members during theorbital movement of the rotary scroll member, the volume of the chambersbeing varied in accordance with the rotation of the rotary scrollmember, the inlet port communicating the chambers for introduction ofthe medium thereto, and the outlet port communicating the chambers forremoval of the medium therefrom;

a base plate fixedly connected to the housing and arranged on one sideof the rotary scroll member;

a first means for defining a plurality of angularly spaced and outwardlyopening first pockets which are integral with the base plate, each ofthe pockets defining a circular peripheral surface extending parallel tothe axis of the shaft and a plane surface extending transverse to theaxis of the shaft;

a second means for defining a plurality of angularly spaced andoutwardly opening second pockets which are integral with the rotaryscroll member, each of the second pockets defining a circular innersurface extending parallel to the axis of the shaft for support, and aplane surface extending transverse to the axis of the shaft, the firstand second means being arranged so as to form a plurality of pairs ofthe first and the second pockets located adjacent to each other, and;

a plurality of connecting means, arranged in each of the pairs of firstand second pockets, for allowing the rotary scroll member to realize anorbital movement while preventing it from rotating about its own axis;

each of said connecting means comprising first and second shoes arrangedin the adjacent pair of first and second pockets, respectively, and aball arranged between the first and second shoes;

the first and second shoes having outer peripheral surfaces in contactwith the inner peripheral surfaces of the first and second pockets,respectively, for receiving a radial force generated during the orbitalmovement;

the first and second shoes having, on first axial ends thereof, a firstgenerally planed surface in contact with the plane surfaces of the firstand second pockets, respectively, and on the second axial ends, havingsecond concave surfaces with which said ball is in contact with forreceiving a thrust force

When an orbital movement of the rotary scroll member is carried out toobtain a compression operation, a resultant generated force is receivedby the base plate of the housing via the rotary scroll member, the shoeson the rotary ring, the balls, and the shoes on the stationary ring. Theshoes between which the balls are held rotate in the respective firstand second holes constructing the pockets, in accordance with theorbital movement of the rotary scroll member, while the shoes are incontact with the opposite plane surface of the first and second pockets,respectively, and while the shoes maintain the contact with thecircumferential surfaces of the first and second holes of the pockets,respectively, and thus the rotary scroll is prevented from rotatingabout its own axis. During the orbital movement of the rotary scrollmember which is not rotated about its own axis, the one pair of shoes incontact with the circular wall in the pair of the holes of the pocketsare, at positions diametrically opposite to each other, subjected toradial forces directed in the opposite direction. The shoes are notinclined in the respective pockets because of the separate constructionof the shoes and ball. Even if the base plate of the rotary scrollmember is bent, the shoes in the rotary scroll member are inclined withrespect to the axis of the balls, so that the shoes on the side of therotary scroll member cannot be inclined with respect to the holestherein. Accordingly, a smooth sliding movement of the shoe in therespective holes is obtained, and thus a smooth orbital movement of therotary scroll member is obtained. Furthermore, a large pressurereceiving area is generated between the shoes and rotary scroll memberand the fixed base plate, thereby causing a pair of shoes and a ball toreceive a large thrust force, which allows a reduction of the number ofunits needed to obtain an orbital movement Furthermore, the work for thepockets, which requires a high precision, can be alleviated

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axial cross-sectional view of the compressor according tothe present invention;

FIG. 2 is an exploded perspective view of essential parts of the presentinvention;

FIG. 3 is a cross-sectional view taken along the line III--III in FIG.1;

FIG. 4 is an enlarged sectional view of a unit for obtaining an orbitalmovement; and,

FIG. 5 is an exploded perspective view showing a balance mechanism inFIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT

In an embodiment of the present invention, reference numeral 1 denotes afront housing and 2 a rear housing and these housings 1 and 2 are joinedtogether via an annular base plate 3 by a not shown fixing means such asbolts and nuts. The front housing 1 is provided with a boss portion 1--1in which a rotating shaft 4 is inserted The rotating shaft 4 has a firstor outer end 4-1 having a small outer diameter and a second or inner end4-2 having a large diameter, and these ends 4-1, 4-2 are supported bythe boss portion 1--1 by a pair of axially spaced roller bearing units30 and 32, respectively. A seal assembly 34 is arranged adjacent to thebearing unit 30 to establish an oil tight seal between the housings 1and 2 and the shaft 4. An eccentric shaft 4a is rigidly connected to theshaft inner end portion 4-2 at the end surface thereof facing the rearhousing 2 so that the eccentric shaft 4a extends, in a cantileverfashion, toward the rear housing. Reference numeral 5 (FIG. 5) denotes abalance weight of sector shape integrally extended from a plate member5-1 and inserted into the pin 4a at a position substantiallydiametrically spaced from the balance weight 5. An eccentric bush member6 is also inserted onto the shaft 4a and a pin 7 having a central axiswhich conforms to that of the rotating shaft 4 is inserted through boththe bush member 6 and the balance plate 5-1. The central pin 7 isextended out of the balance plate 5-1 in such a manner that the pin 7,at an end 7-1 thereof, is projected into a recess 4--4 formed on the endsurface of the large end portion 4-2 of the rotating shaft 4, permittingthe balance weight 5 and bush member 6 to limit an amount of relativerotation Reference numeral 8 denotes a rotary scroll member having adisc-shaped base portion 8a and a boss portion 8-1 projecting from thebase portion 8a toward the front housing 1, the bush member 6 beingrotatably inserted in the boss portion 8-1 via a needle bearing assembly8-2. Further, the rotary scroll member 8 is provided with a scrollportion 8b (FIG. 3) on the other side of the base portion remote fromthe boss portion 8-1. Reference numeral 9 denotes a stationary scrollmember having a base portion 9a fixedly connected to the rear housing 2by an O-ring 9-1 and a scroll portion 9b on a side of the base portion9a facing the rotary scroll member 8. As will be understood, the scrollportions 8b and 9b are arranged to maintain contact with each otherwhile the rotary member 8 realizes an orbital movement about the axis ofthe shaft 4, and as a result, compression chambers S each having avolume which first increases and then decreases during the rotation ofthe shaft 4, are formed between the base portions 8a and 9a and thescroll portions 8b and 9b to carry out an intake and exhaust of thefluid into and from the compression chambers S, respectively.

An intake chamber 1b for a gas as a cooling medium is formed between thefront housing and the plate 3, and an inlet port 1a is formed in thefront housing 1 for an introduction of the cooling medium into thechamber 1b. The chamber 1b is opened to the compression chambers S whenthe volume of the chambers is increasing for an introduction of thecooling medium A delivery chamber 2a for removal of the compressedmedium is formed between the rear housing 2 and the stationary scrollmember 9 The delivery chamber 2a is connected to the compression chamberS when the volume thereof is decreasing, so that the compressed air isintroduced into the chamber 2a via a delivery valve 15, which is a checkvalve located in a passageway 9c connecting the compression chamber andthe chamber 2a. The delivery valve 15 is constructed as a reed valvewhich is provided with a reed member 15a and a stopper member 15b.

Further, the compressor has a plurality of pairs of facing pockets and aconnecting member arranged between the facing pockets. Each of thepockets has, as will be understood, circular holes defining an innerwall extending in parallel to the axis of the shaft 4 and a planesurface extending transversely to the axis of the shaft. Each of theconnecting members is formed by shoes arranged in the respective holesand a ball arranged between the shoes. The construction will now be morefully described

A stationary ring 10 is fixedly connected to a side of the base plate 3facing the rotary scroll member 8. The stationary ring 10 forms aplurality of equiangularily spaced holes 10a (FIG. 2) having a circularshape for delimiting the position of the orbital movement. A rotary ring11 is fixedly connected to the base portion 8a of the rotary scrollmember 8, at the end surface thereof remote from the scroll portion 8b,so that the stationary ring 10 and rotary ring 11 face each other. Therotary ring 11 forms a plurality of equiangularily spaced holes 11a(FIG. 2) having a circular shape for delimiting the position of theorbital movement, and the holes 11a face the corresponding holes 10a inthe stationary ring 10. Each of the holes 10a and 11a has an innercircular surface (or periphery) extending in parallel to the axis of theshaft 4 and each of the ring 3 and the base portion 8a of the rotaryscroll member 8 forms a plane surface 3-1 or 8a-1 (FIG. 4) extendingtransversely to the axis of the shaft 4. The hole 10a or 11a defining aninner circular peripheral wall together with the plane surface 3-1 or8a-1 forms a pocket for storing the connecting member. Namely, aplurality (four) of pairs of facing pockets are formed by the holes 10aand 11a. A shoe 12 having a substantially circular cross-sectional shapeis located in each of the holes 10a in the stationary ring 10; the shoe12 having an outer diameter smaller than the inner diameter of the hole10a. A shoe 13 having a substantially circular cross-sectional shape islocated in each of the holes 11a in the rotary ring 11; the shoe 13having an outer diameter smaller than the inner diameter of the hole11a. A ball 14 is arranged between each of the facing pairs of shoes 12and 13, and thus the facing pair of shoes 12 and 13 and the ball 14arranged therebetween form a connecting member arranged between a pairof facing pockets.

As shown in FIG. 4, the shoe 12 in the stationary ring 10 is formed withspherical abutting end surfaces 12a which are in contact with the endsurface 3-1 of the base plate 3 and are slightly rounded with respect toa plane of the end surface 3-1, i.e., the end surface 12a has a radiusR1 which is very much larger than the radius R of the ball 14.Similarly, the shoe 13 in the rotary ring 11 is formed with sphericalend surfaces 13a which are in contact with the end surface 8a-1 of thebase portion 8a of the rotary scroll member 8 and are slightly roundedwith respect to a plane of the end surface, i.e., the end surface 13ahas a radius which is very much larger than the radius R of the ball 14.At the side remote from the rounded projected surface 12a, the shoe 12has a concave surface having a first and central portion 12b having aradius R2 which is smaller than R and a second portion 12c connected atthe periphery thereof to the first portion 12b and having a radius R3which is larger than R. Namely, a circular projection p₁ is formed at aregion where the central portion 12b is connected to the outer portion12c Similarly, at the side remote from the rounded projected surface13a, the shoe 13 has a concave surface having a first and centralportion 13b having a radius which is smaller than R and a second portion13c connected at the periphery thereof to the first portion and having aradius which is larger than R. Namely, a circular projection p₂ isformed at a region where the central portion 13b is connected to theouter portion 13c. As a result of this arrangement, the ball 14 arrangedbetween the pair of faced shoes 12 and 13 is in contact with the concavesurface at the circular projections p₁ and p₂, respectively, whichpermits the rotary scroll member 8 to realize an orbital movement aboutthe axis of the shaft 4, and the tip ends of the scroll portion 8b and9b of the scroll members 8 and 9 are in contact with the facing surfacesof the base wall portions 9a and 8a of the scroll members 9 and 8.

It should be noted that the radius of the orbital movement of the rotaryscroll member 8 is equal to a sum of the lengths L₁ and L₂ of themovable area of the shoes 12 and 13 in the holes 10a and 11a of therings 10 and 11, respectively The rotation of the shaft 4 causes anorbital movement of the eccentric shaft 4a about the axis of the shaft4, by which the shoes 12 and 13 are rotated in the holes 10a and 11a,respectively, and the facing pair of shoes 12 and 13 are in contact withthe facing pair of the holes 10a and 11a at their circular peripheriesand, respectively, at positions 10a' and 11a' diametrically opposite toeach other, so that rotation of the rotary scroll member 8 around itsown axis is prevented.

The fixed annular base plate 3 and stationary ring 10 are provided witharc-shaped induction passageways 3a and 10b, respectively, aligned witheach other for introducing the coolant gas medium from the inductionchamber 1b, after being introduced via the inlet port 1a, into thecompression chamber via the passageways 3a and 10b and a space betweenthe faced rings 10 and 11. The gas, after compression, is introducedinto the outlet chamber 2a in the rear housing 2 via the delivery valve15 located in the delivery passageway.

As shown in FIG. 4, the shoe 12 has an opening 12d therethrough betweenthe outer convex surface 12a and inner concave surface 12b, andsimilarly, the shoe 13 has an opening 13d therethrough between the outerconvex surface 13a and inner concave surface 13b. As a result,lubrication oil mist in the cooling gas medium is introduced into thebores 12d and 13d via clearances between the plate 3 and convex surface12a and between the base portion 8a and convex surface 13a,respectively, and thus a lubrication of the contacting zones of thefixed plate 3 and the shoe 12, rotary ring 11 and shoe 13, and ball 14and shoes 12 and 13 is obtained A counter compression force andcentrifugal force generated in the rotary scroll member 8 duringrotation thereof are received by the stationary base plate 3 andstationary ring member 10 via the shoes 13, balls 14, and shoes 12,causing a force in the radial direction to be generated in the shoes 13,as shown by an arrow f_(A) in FIG. 4, by way of the rotary ring 11, anda counter force in the radial direction to be generated in the shoes 12,as shown by an arrow f_(B), via the stationary ring 10. Namely, theshoes 12 and 13 are subjected, respectively, to radial forces inopposite directions, but this does not cause any inclination of theshoes 12 and 13 with respect to the opposing sliding surfaces 3-1 and8a-1, due to the construction of the shoes 12 and 13 and balls 14, whichare movable independently of each other Therefore, partial and prematurewear at particular regions, such as the angular regions where the shoes12 and 13 are in contact with the members 3 and 8, respectively, of thestationary ring member 3 and the rotary scroll member 8 is prevented,during the orbital movement. This advantage can be obtained even whenthe base wall 8a of the rotary scroll member 8 is bent Namely, when thebase wall 8a is bent, the general plane of the holes 11a can be slightlyinclined with respect to the vertical axis, and the shoes 13 can slideon the ball 14 about the axis thereof, thereby preventing an inclinationof the shoes with respect to the holes 11a. As a result, as long as thedistances between the bottom of the shoes 12 to the center of the ball14 and between the bottom of the shoe 13 to the center of the ball 14are precisely maintained, a predetermined location of the orbitalmovement of the rotary scroll member 8 in the direction caused when thethrust force is applied thereto is maintained for a prolonged periodwithout change, thereby obtaining a high compression efficiency Itshould be noted that the maintenance of such precise distances as ameans for maintaining the predetermined location of the orbital movementis very easy to obtain when compared with a conventional means formaintaining the predetermined location of the orbital movement by aprecise parallel relationship of the cylindrical bearing members.

When an excessive force in the radial direction is applied to the shoes12 and 13, a thrust force as a counterforce to the above mentionedradial force is generated at the region p₁ between the concave surfaces12b and 12c and the region p₂ between the concave surfaces 13b and 13c,to maintain the desired orbital movement of the scroll member 8. Theshoes 12 and 13 have spherical surfaces 12a and 13a which are very nearto a plane, permitting the contacting areas and contacting surfacepressure with respect to the balls 14 to be reduced, compared with thosein the prior art where a direct contact of the ball is employed,resulting in a reduced number of the units each composed of the shoes 12and 13 and the ball 14. In relation to this effect of reducing thenumber of units, the amount of work for forming the holes 10a and 11a,which requires a high precision, can be reduced, thereby greatlyincreasing the cost efficiency because the number of parts can bereduced and because the necessary work can be reduced The abovementioned effect of reducing the contacting surface pressure alsopermits the necessary number of orbital movement units having a reducedresistance ability to wear, by forming the stationary base plate 3 androtary scroll member 8 from aluminum material, resulting in a reducedweight of the entire compressor.

The present invention is, of course, not limited to the embodiment asdescribed. For example, the surfaces of the shoes 12 and 13 in contactwith the respective balls 14 may have a radius which is larger than theradius R of the ball 14, which also permits the lubrication oil includedin the cooling gas medium to be introduced into an area close to thecenter of the area for receiving the ball, so that an effectivelubrication of the contacting area between the ball 14 and the shoes 12and 13 is obtained. Furthermore, the bottom surfaces of the shoes 12 and13 may be a plane, which allows a large area bottom area of the orbitalmovement delimiting holes 10a and 11a, so that a sufficient lubricationis realized at the regions between the shoes 12 and stationary plate 3and between the shoes 13 and the rotary scroll member 8.

We claim:
 1. A scroll compressor comprising:a housing assembly definingan inlet port for a medium to be compressed and an outlet for removal ofsaid medium; an axially extending drive shaft rotatably supported in thehousing assembly; a stationary scroll member arranged fixedly in thehousing assembly and concentrically to the shaft; a movable scrollmember arranged to be freely rotatable about an axis spaced from theaxis of the drive shaft; the movable scroll member arranged so as torealize an orbital movement with rotation about its own axis; aplurality of chambers formed between the scroll members during theorbital movement of the movable scroll member, the volume of which isvaried in accordance with the orbital movement of the movable scrollmember, the inlet port communicating with the chambers for introductionof the medium thereto and the outlet port communicating with thechambers for removal of the medium therefrom; a base plate fixedlyconnected to the housing and arranged on one side of the movable scrollmember; first means for defining a plurality of angularly spaced andoutwardly opening first pockets which are integral with the base plate,each of the pockets defining a circular peripheral surface extendingparallel to the axis of the shaft and a plate surface extendingtransverse to the axis of the shaft; second means for defining aplurality of angularly spaced and outwardly opening second pockets whichare integral with the movable scroll member, each of the second pocketsdefining a circular inner surface extending in parallel to the axis ofthe shaft for support and a plane surface extending transverse to theaxis of the shaft, the first and second means being arranged so as toform a plurality of pairs of the first and the second pockets locatedadjacent to each other; a plurality of connecting means, arranged ineach pair of the first and second pockets, for allowing the movablescroll member to realize an orbital movement while being prevented fromrotating about its own axis; each of said connecting means comprising afirst and a second shoe arranged in the adjacent pair of the first andsecond pockets, respectively, and a ball arranged between the the firstand second shoes having outer peripheral surfaces in contact with theinner peripheral surfaces of the first and second pockets, respectively,for receiving a radial force generated during the orbital movement; andthe first and second shoes having, on a first axial end thereof, a firstgenerally plane surface in contact with the plane surfaces of the firstand second pockets, respectively, and having, on a second axial endthereof, a second recessed surface with which said ball is in contactfor receiving a thrust force.
 2. A compressor according to claim 1,wherein the first plane surface of the first or second shoe forms aspherically projected surface which is substantially a plane.
 3. Acompressor according to claim 1, wherein the second recessed surface ofthe first or second shoe forms a first spherical portion located at thecenter thereof, having a diameter smaller than that of the ball and asecond spherical portion located around the first portion having adiameter larger than that of the ball, so that a circumferentialprojecting area for contact with the ball is formed between the firstand second portions.
 4. A compressor according to claim 3, wherein atleast the first or second shoe has an opening therethrough having oneend open to the first generally plane surface, and the other end open tothe second recessed surface.
 5. A compressor according to claim 1,wherein said first means for defining the first pockets comprises astationary ring which is separate from and fixedly connected to the baseplate, the stationary ring defining angularly spaced holes therethroughwhich form the inner circular peripheral surface of the first pocket,the base plate forming the plane surface of the first pocket.
 6. Acompressor according to claim 1, wherein said second means for definingthe second pockets comprises a movable ring which is separate from andfixedly connected to the movable scroll member, the rotary ring definingangularly spaced holes therethrough which form the inner circularperipheral surface of the second pocket, the scroll member forming theplane surface of the second pocket.